How to achieve a realistic display with bright colours?
The problem you have here is that the output from the Image Texture is connected to both the Base Color and the Emission inputs of the Principled shader node. The Emission will produce the effect of the glowing screen while the Base Color will also produce an image of the glowing screen - in addition to the Emission but based on any incident light. This means you are effectively including your 'screen' image twice - once for emission and again in response to any light hitting the surface - so it appears &quot;too bright&quot;.
The solution here is to either just use an Emission shader node in place of the Principled shader (Principled is arguably overkill for this situation) or simply disconnect the Base Color and set it to black (or a suitably dark color) to represent the screen when it is 'off'.